All,
Just to give you my chain of events. I'm now on my fourth iPhone 6 Plus - All brand new retail replacements (Not via genius bar). All four of them have been running iOS 8 and then 8.0.2 and unfortunately they have ALL exhibited the same wifi issues :
1. Cannot connect or find any wireless networks - Reboot required
2. Wi-Fi connected with full coverage but no internet or activity - Wi-fi toggle on/off required.
3. When phone is left idle/sleep for long periods of time especially overnight wifi remains connected with full coverage but needs a on/off toggle to restart connection.
4. No speed issues - Always maximum when connected so not facing that issue. 5. They have mainly been on my 5ghz network but similar issues do occur when tried on 2.4ghz.
Now the thing that leads me to believe is that this all down to software and only certain routers/ network setups is that I have got a work 5S that had no issues on i0S 8.0 on my my network but yesterday when I got my latest plus I updated both 5S 6+ to 8.0.2 and configured them exactly the same on my 5Ghz network. This morning they both exhibited the same wifi issues and when coming back after a 6 hours the 5S that had worked perfectly before couldn't detect wifi on my 5G network.
This shows that its a iOS 8 issue that only caused issues with some devices that are connected to a certain routers.
My brothers got the iP6 in his house that has no issues with his router.
So bottom line no need to get hardware replaced 4 times like me, we just have to wait for apple to address the issue in the next update and live with the unstable networks for a bit long which I appreciate shouldn't be the case for devices that we all pay so much for!
Other than that I love my ip6+ - By far the best phone I have ever owned!